Unique Probe Research Articles

Muon spectrometers on China Spallation Neutron Source and its application prospects

<sec>The China Spallation Neutron Source Phase-II Project (CSNS-II) includes the construction of a muon source, namely “Muon station for sciEnce technoLOgy and inDustrY” (MELODY). A muon target station and a surface muon beam line will be completed as scheduled in 2029, making MELODY the first Chinese muon facility. This beam line mainly focuses on the application of muon spin relaxation/rotation/resonance (μSR) spectroscopy. The MELODY also reserves the tunnels for building a negative muon beam line and a decay muon beam line in the future, thereby further expanding the research field to muon-induced X-ray emission (MIXE) elemental analysis and μSR measurements in thick cells, respectively. The two types of material characterization technologies keep their uniqueness in multi-disciplinary researches, and also provide complementary insights for other techniques, such as neutron scattering, nuclear magnetic resonance, and X-ray fluorescence analysis.</sec><sec>The μSR spectroscopy is a mature technology for injecting highly spin polarized muon beams into various types of materials. The subsequent precession and relaxation of muon spin in its surrounding atomic environment reflect the static and dynamical properties of the material of interest, which are then measured by detecting the asymmetric emission of positrons from the decay of those muons, with an average lifetime of approximately 2.2 μs. This enables μSR to develop into a powerful quantum magnetic probe for investigating materials related to magnetism, superconductivity, and molecular dynamics. The combination of a positive muon and an electron is known as muonium, which is a unique and sensitive probe in studying semiconductors, new energy materials, free radical chemistry, etc. As the production of muon beams strongly relies on proton accelerator, only five muon facilities in the world are available for μSR experiments. This limits the large-scale application of muon related sciences. Especially, Chinese researchers face fierce competition and can only apply for precious and limited muon beam time from international muon sources to characterize the key properties of their materials.</sec><sec>The construction of the MELODY muon facility at CSNS-II aims to provide intense and pulsed muon beams for Chinese and international users to conduct their μSR measurements with high quality data in a low repetition rate operation mode. To achieve this goal, as shown in <xref ref-type="fig" rid="Figure1">Fig. 1</xref>, the μSR spectrometer is designed with 1) over 3000 detector units to obtain a sufficient counting rate of 80 Million/h to significantly suppress statistical fluctuations in a short measuring time, 2) a high asymmetry of 0.3 to greatly amplify μSR signals so as to further reduce statistical fluctuations, and 3) extendable low temperature devices to cover most μSR applications and also fulfill experiments with extreme condition requirements.</sec><sec>The MIXE elemental analysis is a type of particle induced X-ray emission (PIXE) technology. Due to the heavier mass of negative muon, the energy of muonic X-ray is around 207 higher than that of X-ray or electron induced fluorescence X-ray. Thus, the MIXE technology is more sensitive to materials with low atomic numbers, and thick samples can be effectively studied without scratching their surfaces. Due to these advantages, the MIXE has been successfully applied to the elemental analysis of cultural heritages, meteorites, Li-ion batteries, etc. MELODY reserves tunnels for negative muon extractions and transport to a MIXE terminal. The MELODY research team is developing a new detection technology with high energy resolution and high counting capability to shorten the measuring time to an acceptable amount based on the 1-Hz repetition rate of muon pulses.</sec><sec>The μSR spectroscopy and MIXE are the two most important application fields of accelerator muon beams. The MELODY muon facility aims to develop and promote these technologies in China by constructing dedicated muon beam lines in CSNS-II and in the future. In this overview, we introduce the principles and advantages of the μSR and MIXE technologies, as well as the physical design and application prospects of the μSR and MIXE spectrometers based on the CSNS-II muon source. Finally, discussions and expectations are made regarding the future upgrade of the CSNS-II muon source’s muon beamline and its broader applications.</sec>

Jet energy redistribution and broadening using hadron+jet measurements in pp and Pb–Pb collisions with ALICE

In this contribution we present measurements of the semi-inclusive distributions of charged jets recoiling from a trigger hadron (hadron+jet) in pp and Pb–Pb collisions, which provide unique probes of medium-induced modification of jet production. We observe that the jet yield at low pT and at large azimuthal angle between the trigger hadron and jet is significantly enhanced in Pb–Pb collisions with respect to pp collisions, which we interpret through comparisons to model calculations.

The FAIR Phase-0 Hyperon Program at HADES

Abstract. Hyperons are a unique probe to study the non-perturbative aspects of the strong interaction. At HADES, they are produced in proton or pion induced reactions at kinetic energies up to 4.5 GeV. Already in the past, HADES has shown its potential for hyperon physics, including λ polarization, λ-N interaction and measurements of the λ(1405) and λ(1520) line-shapes. The HADES detector has recently been extended with a forward detector, partly developed for the PANDA experiment, extending the acceptance for hyperon channels at forward angles. The PANDA@HADES initiative gives the opportunity for an even richer hyperon program. The current main objectives are the production of hyperon resonances, electromagnetic decays of hyperons with special focus on hyperon Dalitz decays and double strangeness production, including a λ – λ interaction study and ξ− production. First results from the ongoing studies promise a successful execution of the program. In the future, there is the possibility for a pion beam experiment with HADES, enabling further hyperon studies.

Blood-based DNA methylation in advanced Nasopharyngeal Carcinoma exhibited distinct CpG methylation signature

The TNM staging system is currently used to detect cancer stages. Regardless, a small proportion of cancer patients recur even after therapy, suggesting more specific molecular tools are required to justify the stage-specific detection and prompt cancer diagnosis. Thus, we aimed to explore the blood-based DNA methylation signature of metastatic nasopharyngeal carcinoma (NPC) to establish a holistic methylation biomarker panel. For the identification of methylation signature, the EPIC BeadChip-based array was performed. Comparative analysis for identifying unique probes, validation, and functional studies was investigated by analyzing GEO and TCGA datasets. We observed 4093 differentially methylated probes (DMPs), 1232 hydroxymethylated probes, and 25 CpG islands. Gene expression study revealed both upregulated and downregulated genes. Correlation analysis suggested a positive (with a positive r, p ≤ 0.05) and negative (with a negative r, p ≤ 0.05) association with different cancers. TFBS analysis exhibited the binding site for many TFs. Furthermore, gene enrichment analysis indicated the involvement of those identified genes in biological pathways. However, blood-based DNA methylation data uncovered a distinct DNA methylation pattern, which might have an additive role in NPC progression by altering the TFs binding. Moreover, based on tissue-specificity, a variation of correlation between methylation and gene expression was noted in different cancers.

Species-specific in situ hybridization confirms arrested development of Henneguya ictaluri in hybrid catfish (Channel Catfish × Blue Catfish) under experimental conditions, with notes on mixed-species infections in clinical cases of proliferative gill disease from Mississippi catfish aquaculture.

Proliferative gill disease (PGD) in Channel Catfish Ictalurus punctatus and hybrid catfish (Channel Catfish × Blue Catfish I. furcatus) is attributed to the myxozoan Henneguya ictaluri. Despite evidence of decreased H. ictaluri transmission and impaired parasite development in hybrid catfish, PGD still occurs in hybrid production systems. Previous metagenomic assessments of clinical PGD cases revealed numerous myxozoans within affected gill tissues in addition to H. ictaluri. The objective of this study was to investigate the development and pathologic contributions of H. ictaluri and other myxozoans in naturally and experimentally induced PGD. Henneguya species-specific in situ hybridization (ISH) assays were developed using RNAscope technology. Natural infections were sourced from diagnostic case submissions in 2019. Experimental challenges involved Channel Catfish and hybrid catfish exposed to pond water from an active PGD outbreak, and the fish were sampled at 1, 7, 10, 12, 14, 16, 18, and 20 weeks postchallenge. Nine unique ISH probes were designed, targeting a diagnostic variable region of the 18S ribosomal RNA gene of select myxozoan taxa identified in clinical PGD cases. Partial validation from pure H. ictaluri, H. adiposa, H. postexilis, and H. exilis infections illustrated species-specific labeling and no cross-reactivity between different myxozoan species or the catfish hosts. After experimental challenge, mature plasmodia of H. ictaluri and H. postexilis formed in Channel Catfish but were not observed in hybrids, suggesting impaired or delayed sporogenesis in the hybridized host. These investigations also confirmed the presence of mixed infections in clinical PGD cases. Although H. ictaluri appears to be the primary cause of PGD, presporogonic stages of other myxozoans were also present, which may contribute to disease pathology and exacerbate respiratory compromise by further altering normal gill morphology. This work provides molecular confirmation and more resolute developmental timelines of H. ictaluri and H. postexilis in Channel Catfish and supports previous research indicating impaired or precluded H. ictaluri sporogony in hybrid catfish.

Highly sensitive and selective off-on fluorescent platform for tricresyl phosphate flame retardant based on twisted intramolecular charge transfer probe

BackgroundTricresyl phosphate (TCP), a typical organic phosphorus flame retardant (OPFR), is an emerging pollutant that causes great concern in recent years due to its high neurotoxicity and reproductive toxicity, etc. Conventional analysis methods for TCP such as gas chromatography and liquid chromatography-tandem mass spectrometry exhibit high sensitivity and accuracy. However, these techniques generally suffer from certain limitations, such as high cost, bulky equipment, time-consuming and operator-dependent properties. Therefore, the establishment of fast and efficient analytical methods for TCP still remains a great challenge. ResultA “turn on” fluorescence sensing strategy for the efficient detection of TCP was established, based on a unique molecular rotor probe of 9-(2,2-dicyanovinyl)-julolidine (DCVJ). The introduction of TCP led to a significant enhancement of the fluorescence intensity of DCVJ. The results show that twisted intramolecular charge transfer (TICT) process might play an important role for this enhancement of fluorescence response via dynamic light scattering measurements and fluorescence lifetime analysis. Further investigations demonstrate that the hydrophobic interaction and conjugation effect between DCVJ and TCP constrain the molecular rotation and vibration of DCVJ, thereby regulating the TICT process, which contribute to this intriguing “turn on” behavior. In view of this, a new sensing platform with excellent performance for TCP was established, which offers quick response time, high selectivity, wide linear range (20–1200 ng mL−1, 1600–8000 ng mL−1), and low detection limit (4.82 ng mL−1). SignificanceThe established new sensing platform for TCP demonstrates the advantages of simplicity, high efficiency, excellent sensitivity and selectivity. The obtained results are also superior to some other previously reported fluorescence methods. This work opens up a new perspective for the efficient detection of emerging OPFRs pollutants.

On the magnetic bistability of small iron clusters used in scanning tunneling microscopy tip preparation

The combination of electron spin resonance with scanning tunneling microscopy has resulted in a unique surface probe with sub-nm spatial and neV energy resolution. The preparation of a stable magnetic microtip is of central importance, yet, at the same time remains one of the hardest tasks. In this work, we rationalize why creating such microtips by picking up a few iron atoms often results in magnetically stable probes with two distinct magnetic states. By using density functional theory, we show that randomly formed clusters of five iron atoms can exhibit this behavior with magnetic anisotropy barriers of up to 73 meV. We explore the dependence of the magnetic behavior of such clusters on the geometrical arrangement and find a strong correlation between magnetic and geometric anisotropy—the less regular the cluster the higher its magnetic anisotropy barrier. Finally, our work rationalizes the experimental strategy of obtaining stable magnetic microtips.

A unique phenothiazine-based fluorescent probe using benzothiazolium as a reactivity regulator for the specific detection of hypochlorite in drinking water and living organisms

As a common disinfectant and an essential reactive oxygen species (ROS), hypochlorite (ClO−) plays vital roles in both water treatment and cell metabolism, but its abnormal level can cause serious harm to human health. Therefore, quantifying ClO− level in drinking water and living organisms is extremely significant. Herein, we decorated different cationic heterocycles on phenothiazine core to construct three fluorescent probes for ClO−. According to the results, only benzothiazolium moiety reasonably adjusted the electron cloud density at sulfur atom of phenothiazine core for the specific oxidation with ClO−, thus endowing the prepared probe PT-BT with a perfect selectivity for ClO−. Meanwhile, PT-BT exhibited a low detection limit (38 nM) and a fast response (within 20 s) toward ClO−. Furthermore, this probe was utilized to fabricate a ready-to-use test strip, which could quantitatively measure ClO− level in real water samples by a portable smartphone sensing platform. Notably, PT-BT targeted mitochondria efficiently, and successfully visualized endogenous ClO− in living cells and zebrafish larvae. Especially, PT-BT was able to monitor the dynamic change of ClO− level in inflammatory mice. These results strongly manifested that probe PT-BT was a promising tool for detecting ClO− in drinking water and living organisms.

A novel activatable fluorescent probe for revealing the dynamic of esterase and viscosity during ferroptosis and DILI

Esterase, a hydrolase, is present in a vast variety of animals, plants, and microbes. It has the potential to promote the hydrolysis of diverse esters while also could function as a valid indicator for assessing cell health. Besides, viscosity is a crucial metric for determining the smooth flow state of various biological macromolecules including proteins, polysaccharides, and lipids in the biological system, which is essential for intracellular signaling and interplay among multiple biological elements. Nevertheless, investigating the relationship between esterase activity, and viscosity in several relevant physiological and pathological processes remains challenging, owing to a lack of an appropriate tool. Herein, EaV is a unique multifunctional fluorescent probe that could measure local microviscosity and esterase in live cells via green and red channels at the same time. The utility of EaV for cell imaging was proven by measuring the esterase and viscosity changes in different cell states. More notably, we studied the changes in esterase and viscosity during erastin-induced ferroptosis, detecting for the first time a considerable reduction in esterase activity and an evident elevation in viscosity. In addition, EaV was used to image the changes of viscosity and esterase in the APAP-induced liver damage model. This fluorescence imaging tool revealed a flexible platform capable of highlighting variations of esterase and viscosity in many cellular processes and was also meaningful in further actually applied in more related early diagnosis and medical intervention.

Impact of inhomogeneous reionization on post-reionization 21-cm intensity mapping measurement of cosmological parameters

ABSTRACT 21-cm intensity mapping (IM) has the potential to be a strong and unique probe of cosmology from redshift of order unity to redshift potentially as high as 30. For post-reionization 21-cm observations, the signal is modulated by the thermal and dynamical reaction of gas in the galaxies to the passage of ionization fronts during the epoch of reionization. In this work, we investigate the impact of inhomogeneous reionization on the post-reionization 21-cm power spectrum and the induced shifts of cosmological parameters at redshifts 3.5 ≲ z ≲ 5.5. We make use of hydrodynamics simulations that could resolve small-scale baryonic structure evolution to quantify H i abundance fluctuation, while seminumerical large box 21cmfast simulations capable of displaying inhomogeneous reionization process are deployed to track the inhomogeneous evolution of reionization bubbles. We discussed the prospects of capturing this effect in two post-reionization 21-cm IM experiments: SKA1-LOW and PUMA. We find the inhomogeneous reionization effect could impact the H i power spectrum up to tens of per cent level and shift cosmological parameters estimation from sub-per cent to tens per cent in the observation of future post-reionization 21-cm IM experiments such as PUMA, while SKA1-LOW is likely to miss this effect at the redshifts of interest given the considered configuration. In particular, the shift is up to 0.0206 in the spectral index ns and 0.0192 eV in the sum of the neutrino masses ∑mν depending on the reionization model and the observational parameters. We discuss strategies to mitigate and separate these biases.

Ratiometric lysosome-targeting luminescent probe based on a coumarin-ruthenium(II) complex for formaldehyde detection and imaging in living cells and mouse brain tissues.

Ratiometric luminescence probes have attracted widespread attention because of their self-calibration capability. However, some defects, such as small emission shift, severe spectral overlap and poor water solubility, limit their application in the field of biological imaging. In this study, a unique luminescence probe, Ru-COU, has been developed by combining tris(bipyridine)ruthenium(II) complex with coumarin derivative through a formaldehyde-responsive linker. The probe exhibited a large emission shift (Δλ>100nm) and good water solubility, achieving ratiometric emission responses at 505nm and 610nm toward formaldehyde under acidic conditions. Besides, ratiometric luminescence imaging of formaldehyde in living cells and Alzheimer disease mouse's brain slices demonstrates the potential value of Ru-COU for the diagnosis and treatment of formaldehyde related diseases.

Miniaturized Endoscopic 2D US Transducer for Volumetric Ultrasound Imaging of the Auditory System.

In this paper, we focus on the carrying out and validation of minimally invasive three-dimensional (3D) ultrasound (US) imaging of the auditory system, which is based on a new miniaturized endoscopic 2D US transducer. This unique probe consists of a 18 MHz 24 elements curved array transducer with a distal diameter of 4 mm so it can be inserted into the external auditory canal. Typical acquisition is achieved by rotating such a transducer around its own axis using a robotic platform. Reconstruction of a US volume from the set of acquired B-scans during the rotation is then performed using scan-conversion. The accuracy of the reconstruction procedure is evaluated using a dedicated phantom that includes a set of wires as reference geometry. Twelve acquisitions obtained from different probe poses are compared to a micro-computed tomographic model of the phantom, leading to a maximum error of 0.20 mm. Additionally, acquisitions with a cadaveric head highlight the clinical applicability of this set up. Structures of the auditory system such as the ossicles and the round window can be identified from the obtained 3D volumes. These results confirm that our technique enables the accurate imaging of the middle and inner ears without having to deteriorate the surrounding bone. Since US is a real-time, wide available and non-ionizing imaging modality, our acquisition setup could facilitate the minimally invasive diagnosis and surgical navigation for otology in a fast, cost-effective and safe way.

Star formation and chemical enrichment in protoclusters

ABSTRACT We examine star formation and chemical enrichment in protoclusters (PCs) using cosmological zoom-in hydrodynamic simulations. We find that the total star formation rate (SFR) in all PC ($\gt 10^{14.4}\, h^{-1}$ M⊙) reaches $\gt 10^4\, \mathrm{M}_\odot \mathrm{yr}^{-1}$ at z = 3, equivalent to the observed PCs. The SFR in the Core region accounts for about 30 per cent of the total star formation in the PC at z ≳ 1, suggesting the importance of the outer regions to reveal the evolution of galaxy clusters. We find that the total SFR of PC is dominated by galaxies with stellar masses $10^{10}\, \le \, (\mathrm{M}_\star /{{\rm M}_{\odot }})\, \le \, 10^{11}$, while more massive galaxies dominate the SFR in the Core. For the chemical abundance evolution, we find that the higher-density region has a higher metallicity and faster evolution. We show that the [O/Fe] versus [Fe/H] relation turns down in the Core at z = 3.4 due to the enrichment of Fe by Type Ia supernovae. We find no environmental effects for the mass–metallicity relations (MZR) or log (N/O) versus 12 + log (O/H) for galaxies. We find that the chemical enrichment in galaxy clusters proceeds faster in the high-redshift universe (z > 1). Our work will benefit future tomographic observations, particularly using PCs as unique probes of accelerated structure formation and evolution in high-density regions of the universe.

Characterizing the initial conditions of heavy-ion collisions at the LHC with mean transverse momentum and anisotropic flow correlations

The study of the initial conditions of relativistic heavy-ion collisions and the subsequent development of hot and dense nuclear matter at the LHC is fundamental for the understanding of the strong nuclear force. The traditional approach of comparing observables with hydrodynamical models based on different initial conditions typically fails to isolate the effects of the initial conditions due to the sensitivity of the observables to the collective behaviour of the expanding system. Correlations of the mean transverse momentum [p T] and the anisotropic flow Fourier coefficients v n have been shown to serve as a unique probe of the initial conditions of the heavy-ion collisions with little to no bias from final state effects.In this talk, correlations between [p T] and v 2 or v 3 are presented as a function of centrality in Pb−Pb and Xe−Xe collisions at TeV and TeV, respectively, measured with ALICE. Additionally, measurements of the higher-order correlation between [p T], v 2, and v 3 is measured for the first time. All of these measurements are compared with hydrodynamical models using IP-Glasma or TRENTo initial conditions. The former is based on Color Glass Condensate effective theory with gluon saturation and the latter is a parameterized model with nucleons as the relevant degrees of freedom. The data is best described by models using IP-Glasma initial conditions, whereas the TRENTo based models fail to describe the data regardless of the parametrization.

Phenothiazine/xanthene-based fluorescent probes for trace and real-time detection of HClO in cells and complex environmental water samples

Hypochlorous acid (HClO) is a vital bioactive molecule. Abnormal levels of HClO can affect the body's immune system and pathological processes, leading to many diseases such as kidney disease and neurodegenerative diseases. Therefore, it is very important and necessary to develop a rapid and sensitive HClO detection method. In this work, we propose a novel phenothiazine-xanthene fluorophore, which has flexible adjustability and outstanding responsiveness to HClO. Using phenothiazine-xanthene fluorophore, a “turn-on” probe 7-ethyl-1,2,3,7-tetrahydrochromeno[2,3-b]phenothiazine-4-carbaldehyde (PTZ-CHO) was designed and synthesized for the trace analysis of HClO. In the presence of HClO, the sulfur atom on phenothiazine is rapidly oxidized to the sulfoxide, and a significant fluorescence enhancement (about 100-fold) was observed. Moreover, the advantages including fast response (<10 s), ultra-high sensitivity (limit of detection = 6 nM), strong specificity, and splendid light stability can all be achieved by PTZ-CHO. Benefitting from these advantages, this unique HClO-responding probe has been successfully applied to the detection of HClO in Hela cells, RAW 264.7 cells, and environmental water samples.

Deep learning assisted jet tomography for the study of Mach cones in QGP

Mach cones are expected to form in the expanding quark-gluon plasma (QGP) when energetic quarks and gluons traverse the hot medium at a velocity faster than the speed of sound in high-energy heavy-ion collisions. The shape of the Mach cone and the associated diffusion wake are sensitive to the initial jet production location and the propagation direction of the parton shower relative to the radial flow because of the distortion caused by the collective expansion of the QGP and the large density gradient. The shape of jet-induced Mach cones and their distortions in heavy-ion collisions provide a unique and direct probe of the dynamical evolution and the equation of state of QGP. However, it is difficult to identify the Mach cone and the diffusion wake in current experimental measurements of final hadron distributions because they are averaged over all possible initial jet production locations and parton-shower propagation directions. To overcome this difficulty, we develop a deep learning assisted jet tomography which uses the full information of the final hadrons from jets to localize the initial jet production positions. This method can help to constrain the initial regions of jet production in heavy-ion collisions and enable a differential study of Mach-cones with different path lengths and orientations relative to the radial flow of the QGP in heavy-ion collisions.

Measuring the cosmic X-ray background accurately

Synthesis models of the diffuse Cosmic X-ray Background (CXB) suggest that it can be resolved into discrete sources, primarily Active Galactic Nuclei (AGNs). Measuring the CXB accurately offers a unique probe to study the AGN population in the nearby Universe. Current hard X-ray instruments suffer from the time-dependent background and cross-calibration issues. As a result, their measurements of the CXB normalization have an uncertainty of the order of sim 15%. In this paper, we present the concept and simulated performances of a CXB detector, which could be operated on different platforms. With a 16-Unit CubeSat mission running for more than two years in space, such a detector could measure the CXB normalization with sim 1% uncertainty.

Interstellar Comets from Post-main-sequence Systems as Tracers of Extrasolar Oort Clouds

Interstellar small bodies are unique probes into the histories of exoplanetary systems. One hypothesized class of interlopers are “Jurads,” exocomets released into the Milky Way during the post-main-sequence as the thermally pulsing asymptotic giant branch (AGB) host stars lose mass. In this study, we assess the prospects for the Legacy Survey of Space and Time (LSST) to detect a Jurad and examine whether such an interloper would be observationally distinguishable from exocomets ejected during the (pre-)main-sequence. Using analytic and numerical methods, we estimate the fraction of exo–Oort Cloud objects that are released from 1–8 M ⊙ stars during post-main-sequence evolution. We quantify the extent to which small bodies are altered by the increased luminosity and stellar outflows during the AGB, finding that some Jurads may lack hypervolatiles and that stellar winds could deposit dust that covers the entire exocomet surface. Next, we construct models of the interstellar small body reservoir for various size–frequency distributions and examine the LSST’s ability to detect members of those hypothesized populations. Combining these analyses, we highlight the joint constraints that the LSST will place on power-law size–frequency distribution slopes, characteristic sizes, and the total mass sequestered in the minor planets of exo–Oort Clouds. Even with the LSST’s increased search volume compared to contemporary surveys, we find that detecting a Jurad is unlikely but not infeasible given the current understanding of (exo)planet formation.

How limiting is optical follow-up for fast radio burst applications? Forecasts for radio and optical surveys

ABSTRACT Fast radio bursts (FRBs) are the first cosmological radio sources that vary on millisecond time-scales, which makes them a unique probe of the Universe. Many proposed applications of FRBs require associated redshifts. These can only be obtained by localizing FRBs to their host galaxies and subsequently measuring their redshifts. Upcoming FRB surveys will provide arcsecond localization for many FRBs, not all of which can be followed up with dedicated optical observations. We aim to estimate the fraction of FRB hosts that will be catalogued with redshifts by existing and future optical surveys. We use the population synthesis code frbpoppy to simulate several FRB surveys, and the semi-analytical galaxy formation code galform to simulate their host galaxies. We obtain redshift distributions for the simulated FRBs and the fraction with host galaxies in a survey. Depending on whether FRBs follow the cosmic star formation rate or stellar mass, 20–40 per cent of CHIME FRB hosts will be observed in an SDSS-like survey, all at z &amp;lt; 0.5. The deeper DELVE survey will detect 63–85 per cent of ASKAP FRBs found in its coherent search mode. CHIME FRBs will reach z ∼ 3, SKA1-Mid FRBs z ∼ 5, but ground based follow-up is limited to z ≲ 1.5. We discuss the consequences for several FRB applications. If ∼1/2 of ASKAP FRBs have measured redshifts, 1000 detected FRBs can be used to constrain Ωbh70 to within ∼10 per cent at 95 per cent credibility. We provide strategies for optimized follow-up, when building on data from existing surveys. Data and codes are made available.

Protoplanetary Disk Chemistry

Planets form in disks of gas and dust around young stars. The disk molecular reservoirs and their chemical evolution affect all aspects of planet formation, from the coagulation of dust grains into pebbles to the elemental and molecular compositions of the mature planet. Disk chemistry also enables unique probes of disk structures and dynamics, including those directly linked to ongoing planet formation. We review the protoplanetary disk chemistry of the volatile elements H, O, C, N, S, and P; the associated observational and theoretical methods; and the links between disk and planet chemical compositions. Three takeaways from this review are: ▪The disk chemical composition, including the organic reservoirs, is set by both inheritance and in situ chemistry.▪Disk gas and solid O/C/N/H elemental ratios often deviate from stellar values due to a combination of condensation of molecular carriers, chemistry, and dynamics.▪Chemical, physical, and dynamical processes in disks are closely linked, which complicates disk chemistry modeling, but these links also present an opportunity to develop chemical probes of different aspects of disk evolution and planet formation.